The source for each curve is indicated by its reference number. Dotted lines are areas of conjecture. The level of detail for change during the Phanerozoic is largely but not entirely a function of geologic preservation and data availability. A non-hostile climate was prerequisite for the evolution of life as we know it. Was there liquid water? Was there crust on which life could take hold? Their chemistry, detected by ion beams just a few microns wide, suggest they formed as part of buoyant crust and in the presence of liquid water Mojzsis et al. Sedimentary rocks deposited in deepwater, below the photic light-penetrated zone, contain muddy, carbon-rich layers with a carbon-isotope signature similar to organic-rich muds of the modern ocean.
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As in the modern ocean, these carbon-rich layers could have accumulated as planktonic bacteria at the surface died and settled to the ocean floor. Not only had life evolved by 3. Life before 3. On the other hand, there is ample evidence that tidal-flat ecosystems survived a period of heavy meteorite bombardment between 3. Whether life arose before or after the LHB, it did so without the help of free oxygen. It is well established from sedimentary rocks and paleosols that free oxygen did not accumulate in the atmosphere until after 2. There was a shadow over those early years — a much dimmer Sun.
So by 3. Most research has looked to something like our modern greenhouse effect as a possible solution. Computer models Kasting , Pavlov et al. The oldest known subaerial sediments — those deposited on land in direct contact with the atmosphere — are preserved in the Barberton terrane South Africa and the Pilbara terrane Australia.
Paleosol: A former or "fossil" soil that is preserved within sedimentary or volcanic deposits. Abramov, O. Microbial habitability of the Hadean Earth during the late heavy bombardment.
Nature , — Allwood, A. Stromatolite reef from the early Archean era of Australia. Anbar, A. A whiff of oxygen before the Great Oxidation Event? Science , — Beerling, D.
Methane and the CH4-related greenhouse effect over the past million years. American Journal of Science , 97— Bekker, A. Oxidative forcing of global climate change; A biogeochemical record across the oldest Paleoproterozoic ice age in North America. Earth and Planetary Science Letters , — Dating the rise of atmospheric oxygen. Berner, R. Geochimica et Cosmochimica Acta 70 , — American Journal of Science , — Blake, R. Phosphate oxygen isotope evidence for a temperate and biologically active Archean ocean.
Nature , — Brocks, J. Archean molecular fossils and the early rise of Eukaryotes.
Byerly, G. An Archean impact layer from the Pilbara and Kaapvaal cratons.
Canfield, D. Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-isotope studies. Late-Neoproterozoic deep-ocean oxygenation and the rise of animal life. Science , 92—95 Catling, D. Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth. Clayton, R. Oxygen isotope exchange between quartz and water. Journal of Geophysical Research 77 , — Des Marais, D. Carbon isotope evidence for the stepwise oxidation of the Proterozoic environment.
Eugster, H. Sodium carbonate-bicarbonate minerals as indicators of PCO2. Journal of Geophysical Research 71 , — Evans, D. Tectonophysics , — Low-latitude glaciations in the Paleoproterozoic era. Farquhar, J. Goldblatt, C. Clouds and the faint young Sun paradox. Climate of the Past 7 , — Bistability of atmospheric oxygen and the Great Oxidation.
Gough, D. Solar interior structure and luminosity variations. Solar Physics 74 , 21—34 Haqq-Misra, J. Revised, hazy methane greenhouse for the Archean Earth. Astrobiology 8 , — Hessler, A. Weathering and sediment generation in the Archean: An integrated study of the evolution of siliciclastic sedimentary rocks of the 3. Precambrian Research , — A lower limit for atmospheric carbon dioxide levels 3.
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Precambrian microflora, Belcher Islands, Canada: Significance and systematics. Journal of Paleontology 50 , — Origin of 3. Geological Society of America Bulletin , — Holland, H. The oxygenation of the atmosphere and oceans.
Changes in Earth’s orbit could explain rise and fall of ancient species
Hren, M. Oxygen and hydrogen isotope evidence for a temperate climate 3. Jaffres, J. The oxygen isotope evolution of sea water; A critical review of a long standing controversy and an improved geological water cycle model for the past 3. Earth-Science Reviews 83 , 83— Kashefi, K. Extending the upper temperature limit for life. Science , Some geologists argue that upwelling magma at spreading centres pushes the plates, whereas others argue that the weight of a portion of a subducting plate one that is forced beneath another may pull the rest of the plate along.
The Ring of Fire is a long horseshoe-shaped earthquake-prone belt of volcanoes and tectonic plate boundaries that fringes the Pacific Ocean basin. For much of its 40,km 24,mile length, the belt follows chains of island arcs such as Tonga and Vanuatu , the Indonesian archipelago , the Philippines , Japan , the Kuril Islands , and the Aleutians , as well as other arc-shaped features, such as the western coast of North America and the Andes Mountains.
The skin has been broken into many different plates because of differences in the density of the rock and differences in subsurface heating between one region and the next. The concept of plate tectonics was formulated in the s. According to the theory, Earth has a rigid outer layer, known as the lithosphere , which is typically about km 60 miles thick and overlies a plastic moldable, partially molten layer called the asthenosphere.
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The lithosphere is broken up into seven very large continental- and ocean-sized plates, six or seven medium-sized regional plates, and several small ones. These plates move relative to each other, typically at rates of 5 to 10 cm 2 to 4 inches per year, and interact along their boundaries, where they converge, diverge, or slip past one another.
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Plate motions cause mountains to rise where plates push together, or converge, and continents to fracture and oceans to form where plates pull apart, or diverge. The theory of plate tectonics is based on a broad synthesis of geologic and geophysical data. It is now almost universally accepted, and its adoption represents a true scientific revolution, analogous in its consequences to quantum mechanics in physics or the discovery of the genetic code in biology. For details on the specific effects of plate tectonics, see the articles earthquake and volcano.
A detailed treatment of the various land and submarine relief features associated with plate motion is provided in the articles tectonic landform and ocean. As the consequence of steady slowdown of earth's rotation, the global ocean would be gradually separated into two oceans. Obviously, the last connection will be broken at the lowest point of the global divide line, located southwest of the Kiribati Islands.
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Since the current western Pacific Ocean is a plane, land would emerge quickly because there would be no chance that water would be exchanged between the two circumpolar oceans after the initial split. The area of final separation between the two oceans would be the simultaneous emerging and drying of territory extending for hundreds of kilometers. While gravity pulls more water toward the Arctic Ocean, the lowlands of Siberia and northern Canada would become submerged. The corresponding movement of water away from the equatorial region combined with the shallow continental shelf waters southeast of Asia and north of Australia will cause land to emerge.
A deepening Arctic Ocean would lead to the further expansion of water over the northern plains of Asia, Europe, and North America. Greenland and Antarctica, despite their high elevations, would become significantly smaller in size. New archipelagos emerge from the southern seas. The Great American Lakes, the biggest freshwater reservoirs in the world, dissolve into the ocean. The slowdown would continue after the separation of the two oceans and cause further migration of the ocean water toward the poles.
Surprisingly despite Antarctica's elevation , the southern polar basin has a larger capacity than the northern one. Given the fixed volume of water in both hemispheres, the more capacious basin of the southern pole would result in an overall lower sea level than the northern ocean. According to volumetric calculation performed with the ArcGIS 3D Analyst extension, the difference between the sea level of the two oceans should be 1, meters.
However, the data accuracy does not warrant this level of precision, so the elevation difference between the sea level of the two oceans used was 1, meters. The series of maps illustationg this article depict the intermittent stages during this migration of the earth's oceans and changes in land extents, topographic elevation, and bathymetric depth caused by the decreasing speed of the earth's rotation. These maps demonstrate the intermediate stages of transitional geography from a rotating to a stationary world. They show the effects of the gradual reduction of centrifugal force from its current level to none, leaving gravity as the only force controlling the ocean's extent.
The actual slowdown of the earth's rotation has been observed, measured, calculated, and theoretically explained. As newer methodologies are developed and more precise instruments are constructed, the exact rate of the slowdown may vary between some sources. Reflecting this very gradual slowing, atomic clocks must be adjusted to solar time by adding a leap second every so often. The first leap second was added in All Antarctica would be under water at this point. The north polar waters and the water over the vast, recently submerged territories in Siberia and Canada would be getting deeper.
At the same time, equatorial waters would be getting more shallow. Large land areas near the equator continue growing and join with each other. By now, nearly all of Canada, Europe, and Russia are covered by a northern circumpolar ocean. Most scientists agree that the solar day related to the speed of rotation is continuously getting longer. This minimal increase of the day length is due mainly to the oceanic tidal friction. When the estimated rate of the slowdown was projected back to past geologic eons, it showed that the length of a day was several hours shorter than today.
Consequently, during the Devonian period million years ago , the earth rotated about 40 more times during one revolution around the sun than it does now. Because the continents have drifted significantly since that time, it is difficult to make estimates of the land versus ocean outlines for that era. However, we can be certain that—with a faster spinning speed in the past—the equatorial bulge of oceanic water was much larger then than it is today. Similarly, the ellipsoidal flattening of the earth was also more significant.